NaClO添加量对TEMPO氧化纳米微纤丝结构与性能的影响

以毛竹粉为原料,采用TEMPO催化氧化联合超声处理制备纳米微纤丝,通过改变Na Cl O与纤维素的质量比,研究了Na Cl O添加量对纳米纤维素的长径比、纤维形态以及羧基含量等特性的影响。结果表明:随着Na Cl O添加量的增加,纳米纤维素羧基含量逐渐提高,长径比增大;当Na Cl O添加量为15 mmol/g时,纳米纤维素羧基含量可高达1.646 mmol/g,横截面直径可达6～10 nm,长径比为273～455;随着纳米纤维素羧基含量的增加,纳米纤维素悬浮液的透光率和剪切黏度不断增大。虽然TEMPO催化氧化程度不断加深,但纳米纤维素的晶型并未遭到破坏,仍然呈现出典型的纤维素I晶体结构,而随着羧基含量的增加,纳米纤维素的结晶度和热稳定性有一定程度的下降。     

端氨基纳米纤维素的制备及对Pb(Ⅱ)的吸附性能研究

以桉木浆为原料,经TEMPO氧化制得羧基化纳米纤维素(CNC)、再经高碘酸钠氧化制得双醛基纳米纤维素(DANC),最后利用二乙烯三胺(DETA)通过席夫碱反应对其进行氨基化改性,得到端氨基纳米纤维素(ANCC)。采用多种方法对纳米纤维素的结构和性能进行了表征,结果表明:DANC含醛基为2.95 mmol/g,ANCC含氨基为1.7 mmol/g,DETA上的氨基成功地接枝到了纳米纤维素链上,使得分子链变长,ANCC的热稳定性提高。ANCC对Pb(Ⅱ)的吸附性能研究表明:室温条件下,当ANCC吸附剂用量为0.1 g,溶液初始质量浓度为400 mg/L且p H值为5.0的条件下吸附3 h,吸附量为210.15 mg/g。吸附过程符合准二级动力学吸附模型和Langmuir等温吸附模型,说明其吸附过程主要为单分子层的化学吸附。     

TEMPO/NaBr/NaClO氧化对纳米微晶纤维素性能的影响

利用TEMPO/NaBr/NaClO体系对硫酸水解漂白硫酸盐浆制备的纳米微晶纤维素(NCC)进行改性制备氧化NCC(TONCC)。采用电导滴定、X射线衍射(XRD)及原子力显微镜(AFM)对改性前后纳米微晶纤维素的表面性能及形貌进行表征,并将其作为造纸增强剂应用于废新闻纸脱墨浆,研究其对浆料强度性能的改善作用。结果表明,TONCC表面引入大量的羧基(0.806 mmol/g),而NCC表面羧基含量仅为0.02 mmol/g,外观由半透明变为透明。TONCC保持了纤维素I的晶型结构,分散性能得到改善,宽度略有减小。将改性前后的纳米微晶纤维素加入到废新闻纸脱墨浆中,与对照样相比,当NCC和TONCC用量为0.6%时,浆料的抗张指数分别提高了8.7%和14.2%;NCC和TONCC用量为0.8%时,撕裂指数提高了约12%。将NCC和TONCC与CPAM联合使用,浆料的抗张指数得到了进一步提升,用量为0.8%时,抗张指数分别为17.35和18.52(N·m)/g,分别比对照样提高了19.6%和27.7%。     

低品质纤维制备微纤化纤维素的研究

以造纸浆渣作为原材料,用高碘酸钠氧化法制备二醛基纤维素(DAC),并利用响应面法优化了DAC的制备工艺,最后对二醛基纤维素进行高压均质化处理得到了微纤化纤维素(MFC)。实验结果表明:在反应温度48℃,氧化剂用量50%,反应时间176 min的最优工艺条件下制备的DAC醛基达到947.38μmol/g。高压均质处理60 min得到的MFC平均粒径为532 nm,结晶度为27.13%,仍然保留有纤维素的基本结构,但热稳定性有所降低。在纸浆中添加5%的MFC可使纸页的抗张强度和耐破指数分别提高了81.40%和47.41%,透气度下降约50%,不透明度稍有提高。     

氧化纤维素的制备及其对碳纳米管的分散效果

以针叶木溶解浆纤维素作为原料,经HNO_3/H_3PO_4/NaNO_2氧化体系选择性氧化后,制备了氧化纤维素(OC)。考察时间、温度及NaNO_2用量对OC的得率及羧基含量的影响,利用傅里叶红外光谱(FT-IR)、X射线衍射仪(XRD)和热重分析仪(TGA)对OC结构和性能进行表征。采用超声波法得到OC水溶液纳米粒子,透射电子显微镜(TEM)和动态光散射(DLS)结果表明:OC在水溶液中可形成均一分散的球形粒子,粒径位于纳米尺寸范围内(30~80 nm)。OC的较优制备工艺条件为:温度为50℃,NaNO_2用量为1.4%,时间为12 h。FT-IR和XRD分析表明:OC分子链中成功引入了羧基官能团,氧化过程中纤维素结晶区和无定形区均受到破坏。相比水和纤维素而言,OC水溶液纳米粒子对碳纳米管(CNT)具有优异的分散效果,其剩余浊度为82.5 NTU,分散效果持续稳定30天以上。     

端氨基超支化聚合物接枝双醛基纳米纤维素的 制备及其对Ni2+的吸附

通过聚合反应制得一种端氨基超支化聚合物(HBP-NH_2),并以桉木浆为原料,经超声波辅助-TEMPO氧化制得羧基化纳米纤维素(CNC)、再经高碘酸钠氧化制得双醛基纳米纤维素(DNC),最后利用HBP-NH_2对DNC进行氨基化改性,得到端氨基超支化聚合物接枝双醛基纳米纤维素(HBPN-DNC),并对反应条件进行优化,当10%的HBP-NH_2溶液加入量为10 mL,反应温度为70℃,反应时间为4 h时N元素质量分数最高,达到6.0%。采用多种方法对纳米纤维素的结构和性能进行了表征,结果表明:氨基成功地接枝到了纳米纤维素链上,使得分子链变长,HBPN-DNC的热稳定性提高。HBPN-DNC对Ni(II)的吸附性能研究表明:室温条件下,当HBPN-DNC吸附剂用量为0.1 g,溶液初始质量浓度为500 mg/L且pH值为5.0的条件下吸附3 h,吸附量为150.21 mg/g。吸附过程符合准二级动力学吸附模型和Langmuir等温吸附模型,说明其吸附过程主要为单分子层的化学吸附。     

微波协同活性炭处理盐酸黄连素废水最佳降解条件的研究

在微波辐射条件下,采用活性炭处理了含盐酸黄连素废水。结果表明:微波催化氧化工艺对盐酸黄连素的处理效果明显优于单纯活性炭吸附与单纯微波辐射工艺。通过正交实验得出微波处理的最佳条件:对于400mg/L的盐酸黄连素模拟水样,活性炭用量0.7g,微波功率700 W,微波时间5min,此时的去除率为89.12%。     

高羧基含量氧化淀粉的制备与表征

通过氧化改性的方法,制备出一种羧基质量分数最高达2.55%的氧化淀粉,系统研究了氧化条件对氧化产物的影响。实验结果表明:10 g淀粉,100 g蒸馏水,糊化温度在80℃,催化剂FeSO4用量为淀粉的1.716%,氧化剂H2O2用量为淀粉的40%,反应温度55℃,反应时间1.5 h时,羧基质量分数最高为2.55%。采用FT-IR、XRD和DSC对氧化淀粉的结构和性能进行了分析,结果表明高羧基含量的氧化淀粉是非晶相,且不同羧基含量的氧化淀粉具有不同的结晶类型;淀粉的前期糊化阶段发生在淀粉的非结晶区,随着氧化的进行,淀粉的非结晶区先被氧化,当氧化程度加大时,氧化又转向结晶区发生反应。     

钼钒同多酸催化降解纤维素制备甲酸的性能研究

以合成的钼钒同多酸Na6[α-Mo6V2O26]·16H2 O为催化剂,对甲苯磺酸为酸催化剂,在水相介质和O2气氛中,考察了钼钒同多酸将纤维素选择性转化为甲酸(FA)的催化性能.实验结果表明:合成的钼钒同多酸催化剂表现出较强的氧化性.在纤维素0.2 g,Na6[α-Mo6V2O26]·16H2O 0.1 g,对甲苯磺酸...     

纤维素C_6位伯羟基的选择性氧化及用于双酚A的吸附研究

采用HNO3/H3PO4-NaNO2氧化体系制备了氧化纤维素,通过红外光谱、固体13C NMR对其结构进行表征,用酸碱中和滴定法测定了产物的羧基含量。同时以氧化纤维素为吸附剂,研究了对水中内分泌干扰物双酚A(BPA)的吸附性能。结果表明:该氧化体系能很好的选择性氧化纤维素的C6位伯羟基,含羧基为20%。在298 K时,氧化纤维素对双酚A最大吸附量为12.67 mg/g,吸附平衡时间为30 min,平衡吸附量随双酚A浓度增加而增加;溶液接近中性及低温条件有利于吸附的进行,溶液中存在电解质则不利于吸附的进行。双酚A的吸附过程属于单分子层吸附,以化学吸附为主,符合准二级动力学方程和Langmuir吸附等温模型。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.